Copper alloy and method of producing same

ABSTRACT

To obtain a copper alloy having a tensile strength of 700 N/mm 2  or more and a conductivity of 60% IACS or more, a copper alloy of the present invention comprises from 0.8 mass % to 1.8 mass % of Co, from 0.16 mass % to 0.6 mass % of Si, and the balance of Cu and unavoidable impurities, in which a mass ratio of Co to Si (Co/Si) is between 3.0 and 5.0; a size of inclusions to be precipitated in the copper alloy is 2 μm or less; and a total volume of the inclusions having a size of between 0.05 μm and 2 μm in the copper alloy is 0.5 vol % or less.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a copper alloy and to a method ofproducing same. In particular, the present invention relates to a copperalloy used for electronic components and to a method of producing same.

2. Description of the Related Art

In lead frames having integrated circuits (IC) mounted thereon,connector terminals to be used in electronic devices, or the like,reductions in thickness of the lead frame and increases in the number ofpins and reductions in terminal pitch have progressed with theminiaturization and multifunctionalization of the devices to be used andwith increases in packaging surface density. For these reasons, there isan increasing demand for reliable connections in packaging of electroniccomponents.

That is, a metal material used for such electronic components must havefurther improved strength because miniaturization of electroniccomponents leads to reductions in thickness. Further, the metal materialmust have further improved conductivity because increases in the numberof pins and reductions in pitch lead to reductions in sectional area.

As a metal material used for electronic components having high strengthand high conductivity, an alloy material containing beryllium (Be) addedto copper (Cu) is conventionally known. Among these alloy materials,there are some having a high tensile strength of 800 N/mm² or more and ahigh conductivity of 50% IACS (International Annealed Copper Standard)or more.

However, in consideration of recent environmental issues, use of analloy material containing Be is now being avoided. Thus, copper alloysreplacing such alloy materials have been attracting attention.

Of the copper alloys, a Cu—Co—Si-based alloy is known to be aprecipitation hardened alloy in which a fine Co₂Si intermetalliccompound is dispersed and precipitated in Cu and serves as a barrieragainst transformation to provide further improved strength andconductivity. It is reported that strength and conductivity can befurther improved by adjusting addition amounts of Co and Si and furtheradding trace amounts of additives.

An example of the conventional Cu—Co—Si-based alloy is a copper alloyused for lead frames containing from 0.4 wt % to 1.6 wt % of Co, from0.1 wt % to 0.5 wt % of Si, the balance of Cu and unavoidable impuritiesand further containing from 0.05 wt % to 1.0 wt % of Zn and from 0.0005wt % to 0.1 wt % of at least one element selected from the groupconsisting of Ca, Y, rare earth elements, Ti, Zr, Hf, V, and Nb (see JP2-277735 A, for example).

Another example thereof is a copper alloy used for electronic andelectric components containing from 0.1 wt % to 3.0 wt % of Co, from 0.3wt % to 1.0 wt % of Si, from 0.3 wt % to 1.0 wt % of Zn, from 0.005 wt %to 0.1 wt % of Mn, from 0.005 wt % to 0.1 wt % of P, the balance of Cuand unavoidable impurities, containing a compound of Co and Si and acompound of Co and P in a parent phase, having an average grain size ofthe parent phase of 20 μm or less, and having an aspect ratio in athickness direction with respect to a rolling direction of between 1 and3 (see JP 9-20943 A, for example).

However, in conventional copper alloys, addition amounts of Co, Si, andother elements and a Co/Si ratio may not be optimized and the copperalloy may not have an appropriate structure. Thus, no conventionalcopper alloy has excellent strength and conductivity. For example,studies have been conducted on the composition of the copper alloy in JP2-277735 A and JP 9-20943 A, but no studies have been conducted oninclusions to be precipitated in the copper alloy. Thus, copper alloyshave problems in that they have no appropriate structure and eitherstrength or conductivity for example, is not sufficient. As a result,conventional copper alloys cannot satisfy a tensile strength of 700N/mm² or more and a conductivity of 60% IACS or more at the same time.

SUMMARY OF THE INVENTION

The present invention has been made in view of solving the problems asdescribed above, and an object of the present invention is to provide acopper alloy having excellent strength and conductivity, in particular,a copper alloy having a tensile strength of 700 N/mm² or more and aconductivity of 60% IACS or more.

Another object of the present invention is to provide a method ofproducing a copper alloy having the properties as described above.

The inventors of the present invention have conducted extensive studiesfor solving the problems as described above, and have conceived that thecomposition of a copper alloy and the size and total amounts ofinclusions to be precipitated in the copper alloy are optimized tooptimize a structure of the copper alloy. Thus, the inventors havecompleted the present invention.

That is, the present invention provides a copper alloy comprising from0.8 mass % to 1.8 mass % of Co, from 0.16 mass % to 0.6 mass % of Si,and the balance of Cu and unavoidable impurities, in which a mass ratioof Co to Si (Co/Si) is between 3.0 and 5.0; size of inclusions to beprecipitated in the copper alloy is 2 μm or less; and total volume ofthe inclusions having a size of between 0.05 μm and 2 μm in the copperalloy is 0.5 vol % or less.

Further, the present invention provides a method of producing a copperalloy including the steps of: (a) melting a copper alloy raw materialincluding from 0.8 mass % to 1.8 mass % of Co, from 0.16 mass % to 0.6mass % of Si, and the balance of Cu and unavoidable impurities andhaving a mass ratio of Co to Si (Co/Si) is between 3.0 and 5.0 to forman ingot, and rolling the ingot; (b) carrying out solution treatmentinvolving heating the rolled material to between 700° C. and 1,000° C.and quenching; (c) carrying out aging treatment by heating an alloymaterial subjected to the solution treatment at between 400° C. and 600°C. for 2 hours to 8 hours; (d) cooling the alloy material subjected tothe aging treatment to at least 380° C. at a cooling rate of between 10°C./h and 50° C./h; and (e) finishing the cooled alloy material by coldrolling.

According to the present invention, an optimum precipitated amount of aCo₂Si compound may be included in the copper alloy, and contents of Coand Si elements remained in a solid solution state may be reduced. Thus,a copper alloy having excellent strength and conductivity, inparticular, a copper alloy having a tensile strength of 700 N/mm² ormore and a conductivity of 60% IACS or more can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a flow chart illustrating a method of producing a copper alloyof the present invention; and

FIG. 2 is a graph showing a relationship between tensile strength andconductivity of copper alloys obtained in Examples 1 and 2 andComparative Examples 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1 (Copper Alloy)

A copper alloy of the present invention is comprised of from 0.8 mass %to 1.8 mass % of Co, from 0.16 mass % to 0.6 mass % of Si, and thebalance of Cu and unavoidable impurities. In a case where Co content isless than 0.8 mass % or Si content is less than 0.16 mass %, asufficient amount of a Co₂Si compound is not formed and desired strengthand conductivity cannot be obtained. In contrast, in the case where theCo content is more than 1.8 mass % or the Si content is more than 0.6mass %, an excess amount of a Co—Si compound phase or a Cu—Co—Si alloyphase is precipitated and desired strength and conductivity cannot beobtained.

Further, a mass ratio of Co to Si (Co/Si) is within a range of between3.0 and 5.0. In the case where the mass ratio is less than 3.0 or morethan 5.0, an excess amount of a Co—Si compound phase or a Cu—Co—Si alloyphase excluding the Co₂Si compound is precipitated and desired strengthand conductivity cannot be obtained.

The unavoidable impurities in the present invention refer to substancesincluded in a general base metal or impurities mixed into the copperalloy during production, and examples thereof include As, Sb, Bi, Pb, S,Fe, O₂, and H₂. Of these, from the viewpoint of improving platingadhesion and soldering properties, the copper alloy of the presentinvention preferably has an O₂ content of 10 ppm or less and an H₂content of 1 ppm or less. In cases where O₂ content is more than 10 ppm,the plating adhesion and soldering properties may degrade. In caseswhere H₂ content is more than 1 ppm, the plating adhesion and solderingproperties may degrade.

Further, inclusions are precipitated in the copper alloy of the presentinvention, and size of the inclusions is 2 μm or less. In cases wherethe size of the inclusions is more than 2 μm, desired strength cannot beobtained and the plating adhesion degrades.

The inclusions in the present invention refer to bulky precipitatedparticles formed during production of the copper alloy. To be specific,inclusions refer to particles of oxides formed through reaction with theatmosphere or particles of undesired Co—Si compound phases or Cu—Co—Sialloy phases excluding the fine Co₂Si compound.

The size of the inclusions refers to diameter of the inclusions if theinclusions are spherical and refers to a shorter diameter or shorterside of the inclusions if the inclusions are elliptical or rectangular.

In the copper alloy of the present invention, total volume of theinclusions having a size of between 0.05 μm and 2 μm in the copper alloyis 0.5 vol % or less. In the case where the total volume of theinclusions is more than 0.5 vol %, desired strength cannot be obtainedand the plating adhesion degrades.

Volume ratio of the inclusions in the copper alloy of the presentinvention can be determined by polishing a section of the copper alloyof the present invention and observing the polished surface with ascanning electron microscope. The volume ratio of the inclusions can bedetermined by specifying an observation region of this case as a regionat a predetermined depth (for example, about 1 μm) or more from anuppermost surface of a sample, integrating the total area of theinclusions in the observation region through image processing, anddetermining the total area by the observation region. To be specific,five arbitrary observation regions of about 100×100 μm are observed, andan average value of area ratios of the inclusions in each observationregion is referred to as the volume ratio of the inclusions.

The copper alloy of the present invention may contain Zn from theviewpoint of improving plating adhesion. Zn has an effect of suppressinginterfacial peeling due to change over time after Sn (tin) plating andSn alloy plating. Zn content is preferably from 0.1 mass % to 1.0 mass%. Zn content within the above range can improve the plating adhesionwithout degrading the strength and conductivity of the copper alloy. Incases where the Zn content is less than 0.1 mass %, the effects ofimproving the plating adhesion through Zn addition may not be obtained.In contrast, in cases where the Zn content is more than 1.0 mass %, theconductivity may degrade.

The copper alloy of the present invention may contain one or moreelements selected from the group consisting of Fe, Ni, P, Sn, Mg, Zr,Cr, and Mn from the viewpoint of further improving the strength. Ofthose, Fe and Ni are more preferred because the elements each have aneffect of improving bending workability through formation of finecrystal grains. Content of the elements is preferably from 0.01 mass %to 0.2 mass % in total. In cases where the content of the elements isless than 0.01 mass %, the effects of improving strength throughaddition of the elements may not be obtained. In contrast, in caseswhere the content of the elements is more than 0.2 mass %, theconductivity may degrade.

(Method of Producing Copper Alloy)

In a conventional method of producing a copper alloy, an ingot obtainedby melting and casting a copper alloy raw material is subjected to hotrolling, then to cold rolling, and the like, thereby forming latticedefects in the copper alloy.

For example, in a method of producing a copper alloy in JP 2-277735 A, acopper alloy raw material is melted and cast in a mold to obtain aningot having desired dimensions. The ingot is subjected to hot rollingat 950° C. and then water cooled immediately. Then, a surface of the hotrolled plate is subjected to milling, to cold rolling to a desiredthickness, and then the resultant is subjected to heat treatment at 500°C. for 1 hour, subjected to rolling to a desired thickness again, andsubjected to stress relief annealing at 300° C. for 1 hour.

In a method of producing a copper alloy in JP 9-20943 A, a copper alloyraw material is melted and cast to obtain an ingot having desireddimensions. Then, the ingot is maintained at 980° C. for 3 hours,subjected to hot rolling, and subjected to milling or pickling andbuffing, to thereby obtain desired dimensions. Next, the resultant issubjected to cold rolling at 85% or more, annealing at between 450° C.and 480° C. for 5 minutes to 30 minutes, cold rolling at 30% or less,and aging treatment at between 450° C. and 500° C. for 30 minutes to 120minutes.

Meanwhile, the inventors of the present invention have conductedextensive studies on a method of producing a copper alloy having theproperties as described above. As a result, the inventors of the presentinvention have found that introduction of lattice defects through coldrolling or the like after hot rolling is not important and cooling ofthe copper alloy subjected to the aging treatment to at least 380° C. ata cooling rate of between 10° C./h and 50° C./h is important forimproving the strength and conductivity of the copper alloy.

To be more specific, the inventors of the present invention have foundthat sufficient lattice defects are introduced into the copper alloythrough quenching after solution treatment, and additional introductionof strain through cold rolling or the like is not needed. Meanwhile,through trials, the inventors of the present invention have found thatcontrol of the cooling rate at between 10° C./h and 50° C./h after theaging treatment without cold rolling or the like provides effects ofprecipitating a sufficient amount of the Co₂Si compound and preventingresidual strain remaining in the copper alloy.

That is, the method of producing a copper alloy of the present inventionincludes the steps of: (a) melting a copper alloy raw material includingfrom 0.8 mass % to 1.8 mass % of Co, from 0.16 mass % to 0.6 mass % ofSi, and the balance of Cu and unavoidable impurities and having a massratio of Co to Si (Co/Si) of between 3.0 and 5.0 to form an ingot, androlling the ingot; (b) carrying out solution treatment involving heatingthe rolled material to between 700° C. and 1,000° C. and quenching; (c)carrying out aging treatment by heating an alloy material subjected tothe solution treatment at between 400° C. and 600° C. for 2 hours to 8hours; (d) cooling the alloy material subjected to the aging treatmentto at least 380° C. at a cooling rate of between 10° C./h and 50° C./h;and (e) finishing the cooled alloy material by cold rolling.

In step (a), the copper alloy raw material may further contain from 0.1mass % to 1.0 mass % of Zn from the viewpoint of improving the platingadhesion. The reasons for the mixing amount are described above.

The copper alloy material may further contain from 0.01 mass % to 0.2mass % of one or more elements selected from the group consisting of Fe,Ni, P, Sn, Mg, Zr, Cr, and Mn in total from the viewpoint of furtherimproving the strength. The reasons for the mixing amount are describedabove.

The copper alloy raw material may have an O₂ content of 10 ppm or lessand an H₂ content of 1 ppm or less from the viewpoint of improving theplating adhesion and soldering properties. The reasons for the contentsare described above. A method of reducing the O₂ and H₂ contents in thecopper alloy raw material is not particularly limited, and aconventional method may be employed. An example of the method includes:methods involving using a deoxidizing agent such as calcium boride; andmethods involving bubbling treatment by using argon gas, nitrogen gas,or the like.

The method of melting the copper alloy raw material is not particularlylimited. The method may involve heating the copper alloy raw material toa melting temperature or higher by using a conventional device such as ahigh frequency melting furnace. The method of casting or rolling is notparticularly limited, and the method may be carried out according toconventional methods.

Note that during step (a), milling may be conducted after the ingot isformed from the viewpoint of removing scales of the ingot. Further,after step (a), annealing may be conducted from the viewpoints ofsoftening the alloy to improve workability, and the like. Methods ofmilling and annealing are not particularly limited, and the methods maybe carried out according to conventional methods.

The solution treatment in step (b) involves heating of the rolledmaterial to between 700° C. and 1,000° C. and quenching the resultant.Heating time is preferably between 1 minute and 60 minutes. A heatingtemperature and heating time within the above ranges allow favorableformation of a solid solution of alloy elements. Methods of heating andquenching are not particularly limited, and the methods may be carriedout according to conventional methods.

The aging treatment in step (c) involves heating of the alloy rawmaterial subjected to the solution treatment at between 400° C. and 600°C. for 2 hours or more and 8 hours or less. A heating temperature andheating time within the above ranges can provide a fine Co₂Si compoundin a precipitated state. Heating methods are not particularly limited,and the method may be carried out according to conventional methods.

Step (d) involves cooling of the alloy raw material subjected to theaging treatment to at least 380° C. at a cooling rate of between 10°C./h and 50° C./h.

A cooling rate within the above range allows sufficient amount of theCo₂Si compound to be precipitated and prevents residual strain remainingin the copper alloy. In cases where the cooling rate is less than 10°C./h, the Co₂Si compound increases in size and desired strength cannotbe obtained. In contrast, in cases where the cooling rate is more than50° C./h, residual strain remains in the copper alloy and the amount ofthe Co₂Si compound that precipitates are reduced due to the strain, sothe Co and Si remain as they are in a solid solution state. Thus,desired strength and conductivity cannot be obtained.

In cases where the cooling temperature is higher than 380° C., anappropriate structure of the copper alloy cannot be obtained and desiredstrength and conductivity cannot be obtained. Note that after thecooling temperature reaches 380° C., since the structure of the copperalloy does not change drastically through the cooling processthereafter, the lower limit of the cooling temperature is notparticularly limited. However, from the viewpoint of stably obtaining acopper alloy having an appropriate structure, the alloy raw material ispreferably cooled to 350° C. at a cooling rate of between 10° C./h and50° C./h.

Step (e) involves cold rolling of the alloy raw material for finishinginto a copper alloy having a desired size. The methods of cold rollingare not particularly limited, and the method may be carried outaccording to conventional methods. After step (e), low temperatureannealing may be conducted from the viewpoint of stress relieving of thecopper alloy. The method of low temperature annealing is notparticularly limited, and the method may be carried out according toconventional methods.

The copper alloy to be obtained by the production method as describedabove is capable of suppressing increase in size of the Co₂Si compoundto be precipitated in the copper alloy and precipitating a sufficientamount of the fine Co₂Si compound, and thus has excellent strength andconductivity.

EXAMPLES

Hereinafter, the present invention will be described specifically withreference to the examples, but the present invention is not limited tothe following examples.

The following properties of copper alloys obtained in the Examples andComparative Examples were evaluated through the following procedures.

(1) Tensile Strength

The tensile strength was evaluated at room temperature in accordancewith JIS Z2241.

(2) Conductivity

The conductivity was evaluated at room temperature in accordance withJIS H0505.

(3) Plating Adhesion

The plating adhesion was evaluated by: subjecting a copper alloy to Snelectroplating to a thickness of 3 μm; heating the copper alloy at 105°C. for 500 hours (500 hours and 1,000 hours in Example 4 alone);conducting a bending and unbending test at 180°; and visually observinga sample surface. In the evaluation: a sample having a plated filmwithout any damage is indicated by ◯; a sample having an unpeeled platedfilm with damage observed is indicated by Δ; and a sample having apeeled plated film is indicated by X.

(4) Bending Workability

The bending workability was evaluated in accordance with JIS Z2248 byconducting a V-bending test at 90° at a bending radius of 0.3 mm andobserving a bent end surface with an optical microscope. In theevaluation: a sample having no wrinkles is indicated by A; a samplehaving small wrinkles is indicated by B; a sample having large wrinklesis indicated by C; a sample having small cracks is indicated by D; and asample having large cracks is indicated by E.

(5) Soldering Property

The soldering property was evaluated by: applying flux to a copper alloysubjected to pickling; immersing the resultant in solder consisting of60 mass % of Sn and 40 mass % of Pb at 235° C. for 5 seconds; andvisually observing a sample surface after pulling the sample out. In theevaluation: a sample having uniform and wet solder on a surface isindicated by ◯; a sample having wet but non-uniform solder withunevenness on a surface is indicated by Δ; and a sample having solderwith a non-wet part on a surface is indicated by X.

Example 1

In Example 1, copper alloys (Products 1 to 3 of the present invention)each containing Cu, Co, Si, and unavoidable impurities in apredetermined ratio were produced following the flow chart shown inFIG. 1. Note that a Cu amount was clarified, but the Cu amount canobviously be estimated from amounts of other components shown.Hereinafter, detailed description will be given of a method of producinga copper alloy by using the flow chart.

First, copper alloy raw materials (such as Cu, Co, and Si) satisfying acomposition ratio shown in Table 1 were prepared. The copper alloy rawmaterials were melted in a high frequency melting furnace and cast intoa plate-like ingot having a thickness of 10 mm (step S1).

Next, milling was conducted for removing scale on an ingot surface (stepS2).

Then, the ingot was subjected to rolling at room temperature, annealingat 800° C., and rolling at room temperature again, to thereby obtain asheet having a thickness of 0.38 mm (step S3).

Then, the sheet was heated at 950° C. for 2 minutes and cooled in waterfor solution treatment (step S4).

The sheet was heated at 500° C. for 4 hours for aging treatment (stepS5).

Then, the sheet was cooled to 380° C. at a cooling rate (to be specific,at the respective cooling rates shown in Table 1) of between 10° C./hand 50° C./h (step S6).

Then, the sheet was subjected to cold rolling (finish rolling), tothereby obtain a copper alloy having a thickness of 0.3 mm (step S7).

Note that the final cold working rate in Example 1 was 21%.

Example 2

In Example 2, copper alloys (Products 4 to 7 of the present invention)each containing Cu, Co, Si, Zn, and unavoidable impurities in apredetermined ratio were produced according to the flow chart shown inFIG. 1.

The production conditions of Example 2 were the same as those ofExample 1. Note that the final cold working rate in Example 2 was 21%.

Comparative Example 1

In Comparative Example 1, copper alloys (Comparative Products 1 to 4)each containing Cu, Co, Si, and unavoidable impurities in a compositionratio departing from a predetermined range were produced according tothe flow chart shown in FIG. 1.

The production conditions of Comparative Example 1 were the same asthose of Example 1. Note that the final cold working rate in ComparativeExample 1 was 21%.

Comparative Example 2

In Comparative Example 2, a copper alloy (Comparative Product 5)containing Cu, Co, Si, Zn, and unavoidable impurities in a predeterminedratio and produced by cooling at a cooling rate of 5° C./h after theaging treatment was produced according to the flow chart shown in FIG.1.

The production conditions of Comparative Example 2 were the same asthose of Example 1 except that the cooling rate after the agingtreatment was changed to 5° C./h. Note that the final cold working ratein Comparative Example 2 was 21%.

Table 1 shows evaluation results of the tensile strength, conductivity,and plating adhesion of the copper alloys obtained in Examples 1 and 2and Comparative Examples 1 and 2. FIG. 2 shows a relationship betweenthe tensile strength and conductivity of the copper alloys.

TABLE 1 Cooling rate Inclusion Maximum Tensile Sample Composition (mass%) after aging volume ratio inclusion size strength Conductivity PlatingKind number Co Si Zn Co/Si (° C./h) (%) (μm) (N/mm²) (% IACS) adhesionPresent invention 1 0.81 0.17 4.8 30 0.4 0.6 700 62 Δ product 2 1.240.29 4.3 30 0.3 0.5 702 61 ◯ 3 1.78 0.58 3.1 10 0.5 0.6 710 60 Δ 4 1280.29 0.5 4.4 30 0.4 0.5 700 61 ◯ 5 1.24 0.28 1.0 4.3 30 0.4 0.5 702 60 ◯6 1.28 0.29 0.5 4.4 10 0.4 0.6 706 62 ◯ 7 1.28 0.29 0.5 4.4 50 0.4 0.5700 60 ◯ Comparative 1 0.60 0.55 1.1 30 0.4 0.5 565 58 ◯ Example 2 2.000.60 3.3 30 0.8 2.5 687 55 X 3 0.80 0.14 5.7 30 0.3 0.5 560 63 ◯ 4 1.800.75 2.4 30 0.8 0.5 700 56 Δ 5 1.28 0.29 0.5 4.4 5 0.7 4.5 682 60 Δ

Table 1 and FIG. 2 reveal that the copper alloys of Products 1 to 7 ofthe present invention each had a maximum inclusion size of 2 μm or less,a volume ratio of the inclusion of 0.5 vol % or less, a tensile strengthof 700 N/mm² or more, and a conductivity of 60% IACS or more.

The copper alloy of Product 2 of the present invention had favorableplating adhesion even though the alloy contained no Zn. Note that in thecopper alloys of Products 1 to 3 of the present invention, plated filmsdid not peel off.

The copper alloys of Products 4 to 7 of the present invention eachcontained Zn and thus had favorable plating adhesion.

Meanwhile, the copper alloys of Comparative Products 1 and 3 each hadinsufficient amounts of Co or Si. Thus, a sufficient amount of Co₂Sicompound was not precipitated, and desired tensile strength was notobtained.

The copper alloy of Comparative Product 2 had too great an amount of Co.An undesired compound phase was formed due to excess Co, and the amountand size of inclusions increased. Thus, desired strength andconductivity were not obtained and plating adhesion was poor. Similarly,the copper alloy of Comparative Product 4 had too great an amount of Si.An undesired compound phase was formed due to excess Si, and desiredconductivity was not obtained.

The copper alloy of Comparative Product 5 had too slow a cooling rateafter the aging treatment. The maximum size of inclusions increased to4.5 μm and the volume ratio thereof increased to 0.7%. Thus, desiredtensile strength was not obtained.

Example 3

In Example 3, copper alloys (Products 8 to 38 of the present invention)each containing Cu, Co, Si, Zn, and unavoidable impurities and one ormore elements selected from the group consisting of Fe, Ni, P, Sn, Mg,Zr, Cr, and Mn in a predetermined ratio were produced following the flowchart shown in FIG. 1. The production conditions of Example 3 were thesame as those of Example 1 except that the composition ratio shown inTable 2 was used and the cooling rate was changed to 30° C./h. Note thatthe final cold working rate in Example 3 was 21%.

Table 2 shows the evaluation results of the tensile strength,conductivity, plating adhesion, and bending workability of the copperalloys obtained in Example 3.

TABLE 2 Sample Composition (mass %) Kind number Co Si Zn Fe Ni P Sn MgZr Cr Mn Co/Si Present invention product 8 1.24 0.29 0.5 0.007 4.3 91.24 0.30 0.5 0.01 4.1 10 1.27 0.29 0.5 0.2 4.4 11 1.24 0.28 0.5 0.0064.4 12 1.24 0.29 0.5 0.01 4.3 13 1.24 0.30 0.5 0.2 4.1 14 1.25 0.29 0.50.006 4.3 15 1.25 0.30 0.5 0.01 4.2 16 1.24 0.29 0.5 0.2 4.3 17 1.240.27 0.5 0.008 4.6 18 1.27 0.28 0.5 0.01 4.5 19 1.23 0.28 0.5 0.2 4.4 201.26 0.29 0.5 0.006 4.3 21 1.24 0.29 0.5 0.01 4.3 22 1.24 0.30 0.5 0.24.1 23 1.24 0.30 0.5 0.006 4.1 24 1.26 0.30 0.5 0.01 4.2 25 1.26 0.270.5 0.2 4.7 26 1.23 0.31 0.5 0.006 4.0 27 1.29 0.31 0.5 0.01 4.2 28 1.240.30 0.5 0.2 4.1 29 1.23 0.27 0.5 0.007 4.6 30 1.25 0.30 0.5 0.01 4.2 311.25 0.28 0.5 0.2 4.5 32 1.25 0.29 0.5 0.15 0.05 4.3 33 1.24 0.29 0.50.1 0.05 4.3 34 1.27 0.29 0.5 0.1 0.05 4.4 35 1.26 0.27 0.5 0.1 0.1 4.736 1.26 0.28 0.5 0.1 0.05 0.05 4.5 37 1.26 0.28 0.5 0.1 0.05 0.05 4.5 381.24 0.29 0.5 0.1 0.05 0.05 4.3 Inclusion Maximum Volume inclusionTensile Sample ratio size strength Conductivity Plating Bending Kindnumber (%) (μm) (N/mm²) (% IACS) adhesion workability Present inventionproduct 8 0.4 0.5 700 60 ◯ B 9 0.4 0.5 703 61 ◯ A 10 0.4 0.5 710 60 ◯ A11 0.4 0.5 701 60 ◯ B 12 0.4 0.5 704 61 ◯ A 13 0.4 0.5 712 60 ◯ A 14 0.40.5 701 60 ◯ B 15 0.4 0.5 705 61 ◯ B 16 0.4 0.5 711 60 ◯ B 17 0.4 0.5700 60 ◯ B 18 0.4 0.5 705 60 ◯ B 19 0.4 0.5 713 60 ◯ B 20 0.4 0.5 700 60◯ B 21 0.4 0.5 704 61 ◯ B 22 0.4 0.5 712 60 ◯ B 23 0.4 0.5 701 60 ◯ B 240.4 0.5 703 60 ◯ B 25 0.4 0.5 710 60 ◯ B 26 0.4 0.5 700 60 ◯ B 27 0.40.5 705 60 ◯ B 28 0.4 0.5 715 60 ◯ B 29 0.4 0.5 700 60 ◯ B 30 0.4 0.5703 61 ◯ B 31 0.4 0.5 713 60 ◯ B 32 0.4 0.5 714 60 ◯ A 33 0.4 0.5 710 60◯ A 34 0.4 0.5 712 60 ◯ B 35 0.4 0.5 712 61 ◯ B 36 0.4 0.5 715 60 ◯ B 370.4 0.5 711 60 ◯ A 38 0.4 0.5 710 60 ◯ A

Table 2 reveals that the copper alloys of Products 8 to 38 of thepresent invention each had a maximum inclusion size of 2 μm or less, aninclusion volume ratio of 0.5 vol % or less, a tensile strength of 700N/mm² or more, and a conductivity of 60% IACS or more.

The copper alloys of Products 8 to 38 of the present invention eachcontained Zn and thus had favorable plating adhesion.

The copper alloys of Products 9-10, 12-13, 32-33 and 37-38 of thepresent invention each had fine crystal grains through addition of apredetermined amount of Fe or Ni, and thus had excellent bendingworkability.

Example 4

In Example 4, a copper alloy (Product 39 of the present invention)containing Cu, Co, Si, and unavoidable impurities in a predeterminedratio and having an O₂ content of 10 ppm or less and an H2 content of 1ppm or less, a copper alloy (Product 40 of the present invention)containing Cu, Co, Si, and unavoidable impurities in a predeterminedratio and having an O₂ content of more than 10 ppm and an H₂ content of1 ppm or less, and a copper alloy (Product 41 of the present invention)containing Cu, Co, Si, and unavoidable impurities in a predeterminedratio and having an O₂ content of more than 10 ppm and an H₂ content ofmore than 1 ppm were produced according to the flow chart shown inFIG. 1. The production conditions of Product 39 of the present inventionwere the same as those of Example 1 except that degassing was conductedby blowing an Ar gas into a molten liquid containing melted rawmaterials. The production conditions of Products 40 and 41 of thepresent invention were the same as those of Example 1. Note that thefinal cold working rate in Example 4 was 21%.

Table 3 shows the evaluation results of the tensile strength,conductivity, plating adhesion, and soldering properties of the copperalloys obtained in Example 4.

TABLE 3 Composition Cooling Inclusion Maximum Conduc- Plating Co Si rateafter volume inclusion Tensile tivity adhesion Sample (mass (mass Co/ O₂H₂ aging ratio size strength (% 500 100 Soldering Kind number %) %) Si(ppm) (ppm) (° C./h) (%) (μm) (N/mm²) IACS) hours hours property Present39 1.28 0.30 4.3 9 0.3 30 0.4 0.5 702 61 ◯ ◯ ◯ inven- 40 1.30 0.31 4.220 0.3 30 0.4 0.5 701 60 ◯ Δ Δ tion 41 1.27 0.29 4.4 50 5 30 0.4 0.5 70060 Δ X Δ product

Table 3 reveals that the copper alloys of Products 39 to 41 of thepresent invention each had a maximum inclusion size of 2 μm or less, aninclusion volume ratio of 0.5 vol % or less, a tensile strength of 700N/mm² or more, and a conductivity of 60% IACS or more. The copper alloyof Product 39 of the present invention had excellent plating adhesionand soldering properties after 500 hours and 1,000 hours. The resultsindicated that the plating adhesion and soldering properties improve byadjusting the O₂ content to 10 ppm or less and the H₂ content to 1 ppmor less in the copper alloy.

As described above, the copper alloy of the present invention hasexcellent strength and conductivity, that is, a tensile strength of 700N/mm² or more, and a conductivity of 60% IACS or more. Further, themethod of producing a copper alloy of the present invention allowsproduction of a copper alloy having a tensile strength of 700 N/mm² ormore and a conductivity of 60% IACS or more.

1. A copper alloy comprising from 0.8 mass % to 1.8 mass % of Co, from0.16 mass % to 0.6 mass % of Si, and the balance of Cu and unavoidableimpurities, wherein a mass ratio of Co to Si (Co/Si) is between 3.0 and5.0; a size of inclusions to be precipitated in the copper alloy is 2 μmor less; and a total volume of the inclusions having a size of between0.05 μm and 2 μm in the copper alloy is 0.5 vol % or less.
 2. A copperalloy according to claim 1, further comprising from 0.1 mass % to 1.0mass % of Zn.
 3. A copper alloy according to claim 1, further comprisingfrom 0.01 mass % to 0.2 mass % of one or more elements selected from thegroup consisting of Fe, Ni, P, Sn, Mg, Zr, Cr, and Mn in total.
 4. Acopper alloy according to claim 1, wherein the copper alloy has an O2content of 10 ppm or less and an H2 content of 1 ppm or less.
 5. Amethod of producing a copper alloy, comprising the steps of: (a) meltinga copper alloy raw material including from 0.8 mass % to 1.8 mass % ofCo, from 0.16 mass % to 0.6 mass % of Si, and the balance of Cu andunavoidable impurities and having a mass ratio of Co to Si (Co/Si) isbetween 3.0 and 5.0 to form an ingot, and rolling the ingot; (b)carrying out solution treatment involving heating the rolled material tobetween 700° C. and 1,000° C. and quenching; (c) carrying out agingtreatment by heating an alloy material subjected to the solutiontreatment at between 400° C. and 600° C. for 2 hours to 8 hours; (d)cooling the alloy material subjected to the aging treatment to at least380° C. at a cooling rate of between 10° C./h and 50° C./h; and (e)finishing the cooled alloy material by cold rolling.
 6. A method ofproducing a copper alloy according to claim 5, wherein the copper alloyraw material further comprises from 0.1 mass % to 1.0 mass % of Zn.
 7. Amethod of producing a copper alloy according to claim 5, wherein thecopper alloy raw material further comprises from 0.01 mass % to 0.2 mass% of one or more elements selected from the group consisting of Fe, Ni,P, Sn, Mg, Zr, Cr, and Mn in total.
 8. A method of producing a copperalloy according to claim 5, wherein the copper alloy raw material has anO₂ content of 10 ppm or less and an H₂ content of 1 ppm or less.